This invention relates generally as indicated to a proportional flow valve and more particularly to a normally-open solenoid controlled flow valve.
A proportional flow valve allows the flow through the valve to be controllably varied as compared to, for example, a standard valve that is either completely open or completely closed. Such a flow valve may include a seal which moves among a closed position whereat it is seated against a valve seat, a fully open position whereat it is removed from the valve seat a predetermined distance, and partially open (or partially closed ) positions whereat it is removed from the valve seat lesser distances. In a solenoid controlled proportional valve, an armature assembly will move the seal, in proportion to the current applied to the solenoid assembly, to selectively change the position of the seal.
A solenoid controlled proportional flow valve is shown in U.S. Pat. No. 5,232,196 to Hutchings et al. (This patent is assigned to the assignee of the present application and its entire disclosure is hereby incorporated by reference.) The valve disclosed in the Hutchings patent is a normally closed solenoid valve wherein an armature assembly holds an elastomeric seal in a closed position when the solenoid assembly is de-energized. The seal is attached to an end of the armature assembly and a spring is positioned between the end of the armature assembly and the seal. This spring-loaded seal configuration helps to compensate for dimensional changes in the elastomeric seal material due to swell and temperature variations.
The normally closed proportional solenoid valve disclosed in the Hutchings patent performs well in many valve situations. However, in other situations, a normally open proportional valve may be more advantageous. For example, in situations where a valve remains fully open most of the time and is only occasionally closed (partially or fully), a normally open valve would allow the solenoid to be energized only during the short periods when the valve is not fully open. For another example, in situations where it is required that the valve remain open during a power outage, a normally open proportional valve meets this requirement without the incorporation of any further failsafe features.
The present invention provides a proportional solenoid controlled flow valve design which is compatible with a normally open arrangement wherein the valve remains fully open unless the solenoid is energized. In this manner, the valve may be used in those situations where a normally open proportional valve is more advantageous than, for example, a normally closed proportional valve.
More particularly, the present invention provides a proportional flow valve comprising a valve body, a seal, a solenoid assembly, and an armature assembly. The valve body includes an inlet, an outlet and a valve seat defining an orifice therebetween. The seal is movable towards and away from the valve seat to a fully open position, a fully closed position, and partially open positions therebetween. The armature assembly is movable at least partially within the solenoid assembly when current is applied to the solenoid. The solenoid assembly moves the armature assembly in proportion to the flow of current and the armature assembly abuttingly engages the seal in the open positions to hold the seal away from the valve seat a distance correspondingly proportionally related to the applied current.
The valve body preferably includes a passageway between the inlet and the outlet and the valve seat is located at one end of the passageway, preferably the end of the passageway adjacent the inlet. An inlet chamber and an outlet chamber are preferably arranged in the valve body so that fluid flows through the inlet to the inlet chamber, through the passageway, into the outlet chamber and through the outlet when the seal is in one of its open positions. The seal is preferably positioned within the inlet chamber so that fluid is blocked from entering the passageway when the seal is in the closed position.
The armature assembly preferably includes a plunger portion and a pin portion. The plunger portion interacts with the solenoid assembly. The pin portion abuttingly engages the seal and extends through the passageway and into the inlet chamber when the seal is in the open positions. The armature assembly additionally or alternatively preferably includes a biasing member which is arranged to resist movement of the armature assembly away from the valve seat. This biasing member may be an annular flat spring positioned adjacent and/or around the armature assembly.
The proportional flow valve preferably further comprises a spring assembly which biases the seal towards the valve seat and the armature assembly allows the spring assembly to seat the seal against the valve seat when in the closed position. The spring assembly preferably includes a spring contained within the valve body, and more preferably a conical spring coaxially aligned with a passageway between the inlet and the outlet.
These and other features of the invention are fully described and particularly pointed out in the claims. The following description and drawings set forth in detail a certain illustrative embodiment of the invention, these embodiments being indicative of but one of the various ways in which the principles of the invention may be employed.